Refrigeration is conventionally generated by compressing and then expanding a refrigerant fluid within a refrigeration circuit. Well known examples of such conventional systems include refrigerators and air conditioners. Typically the refrigerant is a single component fluid which undergoes a phase change at a required temperature from a liquid to a gas thus making its latent heat of vaporization available for cooling purposes. The efficiency of the conventional system can be improved by using a multiple component fluid as the refrigerant which can provide variable amounts of refrigeration over a required temperature range. However, known multiple component fluid refrigeration cycles cannot effectively provide refrigeration over a large temperature range down to colder cryogenic temperatures. Moreover, most well known refrigerant fluids are toxic, flammable and/or ozone depleting.
Accordingly it is an object of this invention to provide multiple component refrigerant fluids which are useful for providing refrigeration down to cryogenic temperatures.